In recent years, small-sizing and capacity expansion of solid electrolytic capacitors which are used for supplying power to digital electronic devices have been strongly demanded. Solid electrolytic capacitors using a metal, such as aluminum, having a valve action are generally widely used, because large capacities can be obtained with small sizes by forming the valve action metal serving as an anode foil into, for example, an etching foil to enlarge a surface of a dielectric.
A solid electrolytic capacitor for applications of small-sizing and large capacity generally has a capacitor element formed by winding an anode foil and a cathode foil, which are formed of a valve-action metal such as aluminum, with a separator interposed therebetween. The solid electrolytic capacitor has a structure in which the capacitor element is impregnated by an electrolyte solution for driving, and housed in a metallic case made of aluminum or a synthetic resin case, and the case is sealed. Note that, not only aluminum but also tantalum, niobium, titanium, and the like are used as anode materials, and the same kinds of metals as the anode materials are used as cathode materials.
In addition, as a solid electrolyte to be used for a solid electrolytic capacitor, manganese dioxide and a 7,7,8,8,-tetracyanoquinodimethane (TCNQ) complex are known, however, recently, there is a technology (Patent Literature 1) focusing on a conductive polymer, such as polyethylenedioxythiophene (which will be referred to as PEDOT below), that has a mild reaction speed and is excellent in adhesion to an oxide coating layer of an anode foil.